Each year, the European Union produces three billion tonnes of waste. This equates to six tonnes of solid waste for every EU citizen, according to Eurostat. A major challenge is findings ways to reduce and reuse a large amount of such waste .

Every day cities in Europe discard a useful nutrient-rich resource that could be used to grow crops. Ironically, we treat and process human wastes while we mine non-renewable phosphate and potassium and we consume fossil fuel to make nitrogen fertiliser.